1. Field of the Invention
The invention relates to apparatus for measuring lateral yarn density distribution.
2. Description of Prior Art
During textile spinning processes, the fibre stream is arranged to form a yarn in many different ways according to the spinning method, machine setting and initial geometry of the fibres in the sliver or roving, This leads to a spun yarn with different structures and mechanical properties. A tracer fibre technique is an effective way to study the fibre path in a yarn. Together with an image analysis algorithm, a large number of tracer fibres can be sampled and a better representation of the yarn structure can be obtained. The yarn cross-section analysis provides some further information on the yarn structure, for example the fibre packing density distribution in a yarn. A very important yarn parameter is related to the highly non-linear torsional and tensile properties of yarn, and the initial lateral compression modulus of fabric and hence fabric handle.
A conventional method of fibre lateral distribution measurement is called the slice cutting method. The procedures of this method include fixing the yarn by means of resin and cutting thin slices of the fixed yarn. The fibres in the yarn cross-section can then be analysed manually or automatically by means of image analysis. The disadvantages of the slice cutting method are that, firstly the yarn structure may be changed in the resin bath, and, secondly, this method is a destructive test. As a result, the same portion of yarn cannot be used for other tests. The method is also tedious and time consuming to carry out.
It is an object of the invention to eliminate the short comings of the conventional method.
According to the invention there is provided a apparatus for measuring the lateral yarn density distribution of a yarn comprising a collimated source of radiation having a selected wavelength within the range of 0.04 nm to 0.25 nm (corresponding to a radiation energy of 30 KeV to 5 KeV), means for holding a length of yarn with a section thereof across a path of the radiation in different rotational orientations between the source and a radiation detector, and a computer programmed to determine the density distribution based on radiation absorption of the yarn in adjacent narrow planes at two or more orientations.
The collimated radiation may be constricted to a path extending over a narrow plane of the section of the yarn and the radiation detector arranged to respond to radiation present beyond the yarn along that narrow path, in which the means for holding the yarn is arranged to move the yarn in steps into different planes in the path of radiation.
The radiation preferably has a wavelength of 0.083 nm (corresponding to a radiation energy of 15 KeV) or 0.15 nm (corresponding to a radiation energy of 8 KeV).
The computer preferably uses a process for determining the yarn density relying on the principle of computed tomography (CT).